[Eoas-seminar] MET Program Seminar at 3:30 PM on Thursday, Nov. 29, 2018

eoas-seminar at lists.fsu.edu eoas-seminar at lists.fsu.edu
Mon Nov 26 20:41:52 EST 2018

Hi all,

Dr. Nirupam Karmakar will give a seminar at 3:30 PM on Thursday, Nov. 29, 2018 at LOV 353. The following is the title and abstract.



Title: The Rhythms of the Indian Monsoon


Two of the most important hydroclimatic features of the Indian Summer Monsoon (ISM) rainfall are its onset/demise and intraseasonal variability (ISV) manifested by the active-break cycles. Understanding the dynamics between these phenomena and their accurate prediction are essential because of their intense socio-economic impact on the enormous agrarian population. ISV is often characterized by two types of intraseasonal oscillations (ISO): low-frequency ISO (LF-ISO) and high-frequency ISO (HF-ISO), with periodicities nearly 20—60-days and 10–20-days, respectively. LF-ISO shows northward propagation convection from the equatorial Indian Ocean. HF-ISO shows a dominant westward propagation from the western Pacific to the Indian region.

An objective definition of local onset/demise of the ISM based on more than a century-long India Meteorological Department (IMD) rain-gauge observation is taken into consideration. The quasi-rhythmic patterns, namely LF- and HF-ISO are identified applying a data-adaptive technique called multichannel singular spectrum analysis. Analysis on the quarter degree IMD data reveals that a large number of local onset (59%) and demise (62%) events occur when they are favored by either of the ISO modes. Further, we performed a case study to understand large-scale association with the onset of the ISM over central India. In 44 of total 58 cases (1948–2005), when central India onset occurred during favorable LF-ISO or HF-ISO phase, they are either linked with a northward propagation of convection from the equator in LF-ISO timescale (28 cases) or westward propagating structures from the western Pacific in HF-ISO timescale (27 cases). Phase-locking between them is important (11 cases).

Lastly, we attempt to link the Indian monsoon to the Atlantic hurricanes in recent time. The Tropical Easterly Jet (TEJ) that originates in the heart of the monsoon (Arabian sea) and makes it way to the eastern Atlantic via all of North Africa. We show that more than 80% cases of hurricanes at Category 4 and above are preceded by upper level diffuence in the TEJ by 0—5 days. A discussion will be made on occurrences of hurricanes over the eastern Atlantic this to the northward moving ISO mode.

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